Immunization to protect against communicable disease is one of the most successful and cost-effective practices of modern medicine. Smallpox has been completely eliminated by vaccination, and the incidence of many other diseases such as polio and diphtheria has been drastically reduced through immunization programs.
Most existing licensed vaccines and vaccines in development, whether based on inactivated viruses or recombinant DNA technology, rely primarily on immune responses to the mature virus, or, in a few examples of experimental, recombinant DNA-based vaccines, immune responses to antigens found in the cell-associated form of the virus, or virus-infected cells. Both the killed virus and attenuated virus approaches on the one hand and the recombinant DNA approaches on the other hand have their advantages and their limitations. While the cell culture and embryonated egg methods are used to grow whole virus very inexpensively, they are not very efficient methods for the commercial production of the viral precursor proteins found in the infected cells and the cell-associated forms of the virus. Production of viral vaccine proteins in insect or mammalian cells by recombinant methods is generally more expensive on a per milligram protein basis than cell culture and egg production methods.
Adverse reactions from vaccines may arise from impurities or from biologic properties of the vaccine proteins (antigens) responsible for conferring protective immunity. For example, the contaminating egg protein present in the licensed influenza vaccines may be largely responsible for the adverse reactions associated with these products.
Current production of human influenza vaccine takes place primarily in fertile chicken eggs. Several hundred million of eggs worldwide are used each year to produce vaccine for the influenza season. The current production cycle (beginning with identification of the anticipated virus strains expected to be present in the forthcoming influenza season) is many months long. The current production processes that use fertile eggs is labor intensive, expensive and fraught with variables, such as the seasonal availability and variation of properties of the eggs.
It would therefore be desirable to provide improved virus vaccine preparations that do not exhibit as many of the limitations and drawbacks observed with the use of currently available vaccines.